- ID:
- ivo://CDS.VizieR/J/ApJ/780/34
- Title:
- H_160_-selected catalog of galaxies in the HUDF
- Short Name:
- J/ApJ/780/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of an H_160_-selected photometric catalog of galaxies in the Hubble Ultra-Deep Field, using imaging from the WFC3/IR camera on the Hubble Space Telescope in combination with archival ultraviolet, optical, and near-infrared imaging. Using these data, we measure the spectral energy distributions of ~1500 galaxies to a limiting H_160_ magnitude of 27.8, from which we fit photometric redshifts and stellar population estimates for all galaxies with well-determined Spitzer IRAC fluxes, allowing for the determination of the cumulative mass function within the range 1<z<6. By selecting samples of galaxies at a constant cumulative number density, we are able to explore the coevolution of stellar masses and star formation rates (SFRs) for progenitor galaxies and their descendants from z~6. We find a steady increase in the SFRs of galaxies at constant number density from z~6 to z~3, accompanied by gradually declining specific star formation rates (sSFRs) during this same period. The peak epoch of star formation is also found to shift to later times for galaxies with increasing number densities, in agreement with the expectations from cosmic downsizing. The observed SFRs can fully account for the mass growth to z~2 among galaxies with cumulative number densities greater than 10^-3.5^Mpc^-3^. For galaxies with a lower constant number density (higher mean mass), we find the observed stellar masses are ~three times greater than that which may be accounted for by the observed star formation alone at late times, implying that growth from mergers plays an important role at z<2. We additionally observe a decreasing sSFR, equivalent to approximately one order of magnitude, from z~6 to z~2 among galaxies with number densities less than 10^-3.5^Mpc^3^, along with significant evidence that at any redshift the sSFR is higher for galaxies at higher number density. The combination of these findings can qualitatively explain the previous findings of a specific star formation rate plateau at high redshift. Tracing the evolution of the fraction of quiescent galaxies for samples matched in cumulative number density over this redshift range, we find no unambiguous examples of quiescent galaxies at z>4.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/414/3052
- Title:
- HST/ACS Coma Cluster Survey. VI.
- Short Name:
- J/MNRAS/414/3052
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using deep, high-spatial-resolution imaging from the Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) Coma Cluster Treasury Survey, we determine colour profiles of early-type galaxies in the Coma cluster. From 176 galaxies brighter than MF814W(AB)=-15mag that are either spectroscopically confirmed members of Coma or identified by eye as likely members from their low surface brightness, data are provided for 142 early-type galaxies. Typically, colour profiles are linear against log (R), sometimes with a nuclear region of distinct, often bluer colour associated with nuclear clusters. Colour gradients are determined for the regions outside the nuclear components. We find that almost all colour gradients are negative, both for elliptical and for lenticular galaxies. Most likely, earlier studies that report positive colour gradients in dwarf galaxies are affected by the bluer colours of the nuclear clusters, underlining that high-resolution data are essential to disentangle the colour properties of the different morphological components in galaxies. Colour gradients of dwarf galaxies form a continuous sequence with those of elliptical galaxies, becoming shallower towards fainter magnitudes. Interpreting the colours as metallicity tracers, our data suggest that dwarfs as well as giant early-type galaxies in the Coma cluster are less metal rich in their outer parts. We do not find evidence for environmental influence on the gradients, although we note that most of our galaxies are found in the central regions of the cluster. For a subset of galaxies with known morphological types, S0 galaxies have less steep gradients than elliptical galaxies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/445/2385
- Title:
- HST/ACS Coma Cluster Survey. X.
- Short Name:
- J/MNRAS/445/2385
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present scaling relations between structural properties of nuclear star clusters and their host galaxies for a sample of early-type dwarf galaxies observed as part of the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) Coma Cluster Survey. We have analysed the light profiles of 200 early-type dwarf galaxies in the magnitude range 16.0<m_F814W_<22.6mag, corresponding to -19.0<M_F814W_<-12.4mag. Nuclear star clusters are detected in 80 percent of the galaxies, thus doubling the sample of HST-observed early-type dwarf galaxies with nuclear star clusters. We confirm that the nuclear star cluster detection fraction decreases strongly towards faint magnitudes. The luminosities of nuclear star clusters do not scale linearly with host galaxy luminosity. A linear fit yields L_nuc_~L_gal_^0.57^+/-0.05. The nuclear star cluster-host galaxy luminosity scaling relation for low-mass early-type dwarf galaxies is consistent with formation by globular cluster (GC) accretion. We find that at similar luminosities, galaxies with higher Sersic indices have slightly more luminous nuclear star clusters. Rounder galaxies have on average more luminous clusters. Some of the nuclear star clusters are resolved, despite the distance of Coma. We argue that the relation between nuclear star cluster mass and size is consistent with both formation by GC accretion and in situ formation. Our data are consistent with GC inspiralling being the dominant mechanism at low masses, although the observed trend with Sersic index suggests that in situ star formation is an important second-order effect.
- ID:
- ivo://CDS.VizieR/J/ApJ/888/31
- Title:
- HST/ACS observations and SFH of Antlia B
- Short Name:
- J/ApJ/888/31
- Date:
- 25 Oct 2021 10:03:38
- Publisher:
- CDS
- Description:
- A census of the satellite population around dwarf galaxy primary hosts in environments outside the Local Group is essential to understanding {Lambda} cold dark matter galaxy formation and evolution on the smallest scales. We present deep optical Hubble Space Telescope imaging of the gas-rich, faint dwarf galaxy Antlia B (M_V_=-9.4) --a likely satellite of NGC 3109 (D=1.3Mpc)-- discovered as part of our ongoing survey of primary host galaxies similar to the Magellanic Clouds. We derive a new tip of the red giant branch distance of D=1.35+/-0.06Mpc (m-M=25.65+/-0.10), consistent with membership in the nearby NGC 3109 dwarf association. The color-magnitude diagram (CMD) shows both a prominent old, metal-poor stellar component and confirms a small population of young, blue stars with ages <~1Gyr. We use the CMD fitting algorithm MATCH to derive the star formation history (SFH) and find that it is consistent with the typical dwarf irregular or transitional dwarf galaxy (dTrans) in the Local Group. Antlia B shows relatively constant stellar mass growth for the first ~10-11Gyr and almost no growth in the last ~2-3Gyr. Despite being gas-rich, Antlia B shows no evidence of active star formation (i.e., no H{alpha} emission) and should therefore be classified as a dTrans dwarf. Both Antlia B and the Antlia dwarf (dTrans) are likely satellites of NGC3109, suggesting that the cessation of ongoing star formation in these galaxies may be environmentally driven. Future work studying the gas kinematics and distribution in Antlia B will explore this scenario in greater detail. Our work highlights the fact that detailed studies of nearby dwarf galaxies in a variety of environments may continue to shed light on the processes that drive the SFH and evolution of dwarf galaxies more generally.
- ID:
- ivo://CDS.VizieR/J/ApJ/864/111
- Title:
- HST/ACS one-year observations of M51 stars
- Short Name:
- J/ApJ/864/111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar photometric variability offers a novel probe of the interior structure and evolutionary state of stars. Here we present a census of stellar variability on day to decade timescales across the color-magnitude diagram (CMD) for 73000 stars brighter than M_I,814_=-5 in the Whirlpool Galaxy (M51). Our Cycle 24 Hubble Space Telescope (HST) program acquired V606- and I814-band images over 34 epochs spanning 1 year with pseudo-random cadences enabling sensitivity to periods from days to months. We supplement these data with archival V- and I-band HST data obtained in 1995 and 2005, providing sensitivity to variability on decade timescales. At least 50% of stars brighter than M_I,814_=-7 show strong evidence for variability within our Cycle 24 data; among stars with V_606_-I_814_>2 the variability fraction rises to ~100%. Large amplitude variability (>0.3mag) on decade timescales is restricted to red supergiants (RSGs) and very luminous blue stars. Both populations display fairly smooth variability on month-year timescales. The Cepheid instability strip is clearly visible in our data, although the variability fraction within this region never exceeds ~10%. The location of variable stars across the CMD broadly agrees with theoretical sources of variability, including the instability strip, RSG pulsational instabilities, long-period fundamental mode pulsations, and radiation-dominated envelopes in massive stars. Our data can be used to place stringent constraints on the precise onset of these various instabilities and their lifetimes and growth rates.
- ID:
- ivo://CDS.VizieR/J/ApJ/681/290
- Title:
- HST/ACS photometry in the SMC
- Short Name:
- J/ApJ/681/290
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present our photometric study of the stellar association NGC 602 in the wing of the Small Magellanic Cloud (SMC). The data were taken in the filters F555W and F814W using the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope (HST). Photometry was performed using the ACS module of the stellar photometry package DOLPHOT. We detected more than 5500 stars with a magnitude range of 14<~m_555_<~28mag. Three prominent stellar concentrations are identified with star counts in the observed field, the association NGC 602 itself, and two clusters, one of them not being currently in any known catalog. The color-magnitude diagrams (CMDs) of both clusters show features typical for young open clusters, while that of the association reveals bright main-sequence (MS) and faint pre-main-sequence (PMS) stars as the members of the system.
- ID:
- ivo://CDS.VizieR/J/A+A/638/A111
- Title:
- HST/ACS photometry of KKH22 and KKH34
- Short Name:
- J/A+A/638/A111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present observations with the Advanced Camera for Surveys on the Hubble Space Telescope of the nearby dwarf spheroidal galaxy KKH 22 = LEDA 2807114 in the vicinity of massive spiral galaxy IC 342. We derived its distance of 3.12+/-0.19Mpc using the Tip of Red Giant Branch method. We also use the 6-m BTA spectroscopy to measure a heliocentric radial velocity of globular cluster in KKH 22 to be +30+/-10km/s. The dSph galaxy KKH 22 has the V-band absolute magnitude of -12.19mag and the central surface brightness {mu}_v,0_=24.1mag/arcsec^2^. Both the velocity and the distance of KKH 22 are consistent with the dSph galaxy being gravitationally bound to IC 342. Another nearby dIr galaxy, KKH 34, with a low heliocentric velocity of +106km/s has the TRGB distance of 7.28+/-0.36Mpc residing in the background respect to the IC 342 group. KKH 34 has surprisinly high negative peculiar velocity of -236+/-26km/s.
- ID:
- ivo://CDS.VizieR/J/A+A/507/1375
- Title:
- HST/ACS VI data of M31 globular clusters
- Short Name:
- J/A+A/507/1375
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the aim of increasing the sample of M31 clusters for which a colour-magnitude diagram is available, we searched the HST archive for ACS images containing objects included in the Revised Bologna Catalogue of M31 globular clusters (RBC Version 3.5 available at: http://www.bo.astro.it/M31). Sixty-three such objects were found. We used the ACS images to confirm or revise their classification and were able to obtain useful CMDs for 11 old globular clusters and 6 luminous young clusters. We obtained simultaneous estimates of the distance, reddening, and metallicity of old clusters by comparing their observed field-decontaminated CMDs with a grid of template clusters of the Milky Way. We estimated the age of the young clusters by fitting with theoretical isochrones.
- ID:
- ivo://CDS.VizieR/J/ApJ/865/33
- Title:
- HST and Chandra obs. of the GLIMPSE-C01 star cluster
- Short Name:
- J/ApJ/865/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of Hubble Space Telescope and Chandra X-Ray Observatory observations of the GLIMPSE-C01 (hereafter GC01) star cluster. Color-magnitude and color-color diagrams suggest a cluster age of >~2Gyr up to ~10Gyr (dependent on GC01's metallicity), a distance of 3.3-3.5kpc, and strong differential reddening with A_V_=14-22. After performing astrometric corrections, we find that nine of the 15 X-ray sources have at least one near-infrared (NIR) counterpart within the 2{sigma} Chandra positional error circles. However, given the very high density of NIR sources in the cluster, most of these counterparts are likely due to chance coincidence. We jointly analyze the X-ray and NIR properties to assess the likelihood of true associations. Based primarily on their X-ray properties, we identify a low-mass X-ray binary candidate (source X2), a cataclysmic variable (CV) candidate (source X1), and an active binary (AB) candidate (source X9). Source X11 is detected during an X-ray flaring episode with a flare luminosity (L_X_=2.1x10^33^erg/s) and has a quiescent luminosity L_X_<8.0x10^30^erg/s, in 0.5-8keV at the distance of GC01, suggesting that the source is either an AB or CV. We also discuss the limits on an intermediate-mass black hole at the center of GC01 and the challenges of X-ray source classification imposed by the limitations of the existing data and instrumentation along with future prospects in the James Webb Space Telescope era.
- ID:
- ivo://CDS.VizieR/J/ApJ/738/186
- Title:
- HST and DEIMOS measurements of NGC 2419 stars
- Short Name:
- J/ApJ/738/186
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis of a kinematic data set of stars in the globular cluster NGC 2419, taken with the DEep Imaging Multi-Object Spectrograph at the Keck II telescope. Combined with a reanalysis of deep Hubble Space Telescope and Subaru Telescope imaging data, which provide an accurate luminosity profile of the cluster, we investigate the validity of a large set of dynamical models of the system, which are checked for stability via N-body simulations.
